WO2013040862A1

WO2013040862A1 - Method for producing aluminium oxide by processing fly ash with ammonia process

Info

Publication number: WO2013040862A1
Application number: PCT/CN2012/001289
Authority: WO
Inventors: 李来时; 廖新勤; 刘瑛瑛
Original assignee: 中铝国际工程股份有限公司
Priority date: 2011-09-24
Filing date: 2012-09-21
Publication date: 2013-03-28
Also published as: CN102358623A

Abstract

The present invention relates to a method for producing aluminium oxide using industrial solid wastes, and especially relates to a method for producing aluminium oxide by processing fly ash with an ammonia process. The method comprises the following steps: milling raw materials, calcining same to obtain a wrought material, dissolution of the wrought material, recovery by ammonia gas, separation and scrubbing of high silicon slag, decomposition of the aluminium ammonium sulfate solution, separation and scrubbing of the crude aluminium oxide, evaporation of the ammonium sulfate solution and Bayer process treatment. The products are aluminium oxide of metallurgical grade, high silicon slag and high iron slag, wherein the high silicon slag can be used as the raw material for producing carbon white, silica gel and high silicon products, and the high iron slag can be used as the raw material for iron-making. The present invention does not need any aid, can effectively extract aluminium oxide from fly ash, and the extraction rate of aluminium oxide can reach more than 90%, thereby achieving comprehensive utilization of fly ash.

Description

Method for treating alumina from fly ash by ammonia method

The present invention relates to a process for producing alumina using industrial solid waste treatment, and more particularly to a process for producing alumina from fly ash by an ammonia process. Background technique

Fly ash is solid waste discharged from coal-fired power plants. In 2008, China's annual output of fly ash reached 300 million tons, and the total stock of fly ash in China was more than 50 billion tons. The discharge of a large amount of fly ash not only encroaches on a large amount of land, but also seriously pollutes the environment, which constitutes both ecological and environmental damage. Therefore, the comprehensive utilization of fly ash has great practical significance and long-term strategic significance. Similarly, China is a country where bauxite resources are not rich. According to the current growth rate of alumina production and the speed of bauxite mining, even considering the prospective reserves, the useful life of bauxite in China is difficult to reach 30 years. Therefore, there are two ways to solve this resource crisis: First, rational use of existing bauxite resources; Second, actively seek and use other aluminum-containing resources. Alumina is one of the main components of fly ash, and its mass fraction is generally 15% to 40%, and the highest is 58%. Therefore, the research work on extracting alumina from fly ash can solve the pollution of fly ash and turn waste into treasure.

At present, the methods for extracting alumina from fly ash mainly include alkali method, acid method and ammonia method. More mature ones are limestone sintering and soda lime sintering, both of which are commonly referred to as alkali processes. In December 2004, the Inner Mongolia Autonomous Region Science and Technology Department held a scientific and technological achievement appraisal meeting for the “Fly Ash Extraction and Alumina Co-production Cement Industrialization Technology” project researched and developed by Mengxi High-tech Group Co., Ltd., using limestone sintering method, Datang International Co., Ltd. uses a modified soda lime sintering process to treat fly ash to produce alumina. However, there are some problems in the extraction of alumina from fly ash by alkaline method. It is mainly the silicon calcium strontium produced by the sintering method. It can only be used as cement raw material. It produces several times the silicon calcium of fly ash for every ton of alumina produced. Slag, and cement has its corresponding sales radius. If there is no large-scale cement industry support in the local area, it will cause secondary pollution. 2 The sintering method only extracts the alumina in the fly ash, and its silica utilization value is low. 3 Sintering treatment of coal ash equipment has large investment, high energy consumption and high cost.

Since the aluminum-to-silicon ratio of fly ash is very low, it is generally less than 1, so it is more reasonable to use the acid method to treat fly ash. An aluminum salt formed by the reaction of an acid or an acidic compound with alumina in fly ash. The aluminum salt dissolves and enters the solution. The silicon does not react with the acid or the acidic compound, and remains completely in the solid. In the slag. Acid treatment of fly ash can overcome the shortcomings of the sintering method, and will not produce more solid waste than the raw material fly ash. After the alumina is extracted, the silica will be enriched, and the content of the slag can reach 80~90% ( According to the alumina extraction rate of 85%, this is more conducive to its utilization. The alumina extraction rate in fly ash refers to the ratio of alumina dissolved in the solution to alumina in the fly ash after calcination. The acid method includes a sulfuric acid method and a hydrochloric acid method, wherein the fluorine ammonia-assisted acid leaching method is relatively mature, and a high alumina extraction rate can be obtained, but due to the addition of fluorine ammonia, ammonia gas and hydrogen fluoride toxic gas are generated in the production process. , adversely affecting the surrounding environment and labor safety, and has not been industrialized due to problems such as severe corrosion of acid equipment and high cost.

The ammonia method is a mixed calcination method of ammonium sulfate fly ash, and has the following advantages: 1. The high silicon slag after extracting alumina can be used as a high silicon filler after being processed, and can also be used for preparing a silicon series product such as white carbon black, since no alkali can be used. It is directly used in the production of cement; the high iron slag produced in the process of extracting alumina can be used as the raw material for iron making, and the aluminum, silicon and iron in the fly ash are effectively utilized; 2 the reaction system is a weak acid system, and the equipment is easier to solve, which is beneficial to the process. Industrialization; 3 The preparation process is a reduction process with a small amount of slag. However, there are some shortcomings and problems in the ammonia method currently formed: For example, the patent CN100457628C "Extracting alumina from fly ash and co-production of white carbon black" mentioned that it is activated at 600~700 °C for 1~2h, so It may be that the extraction rate of alumina in fly ash is high, but the heating and heating process of fly ash is high in energy consumption, and the subsequent treatment of ammonia or ammonia precipitated by the "alkaline dissolved carbon" process is used. A mixture of ferric hydroxide, the alumina produced in this way is powdered alumina can not meet the requirements of the electrolytic aluminum industry; in some current patents, it is neglected that ammonia or ammonia precipitated from aluminum hydroxide contains sulfate, sulfate. Treatment with lye can cause a large loss of alkali.

In order to solve the above technical problems, the present invention provides a method for producing alumina by treating fly ash by ammonia method, aiming at eliminating high-energy calcination activation without adding any auxiliary agent, and ensuring that the alumina extraction rate in fly ash is not lowered. The Bayer process is used to treat the mixture of aluminum hydroxide and ferric hydroxide obtained by precipitation of ammonia or ammonia gas to obtain sand-like alumina which meets the requirements of electrolytic aluminum, and adopts advanced aluminum hydroxide desulfurization technology to make it alkali-soluble. Or reduce the loss of alkali during the Bayer process.

In order to achieve the above object, the present invention provides a method for producing alumina by fly ash by an ammonia process, which comprises the steps of:

Raw material preparation: mixing fly ash with ammonium sulfate to prepare raw material, wherein the weight ratio of ammonium sulfate to alumina in fly ash is 4.5 - 8:1; Clinking of clinker: The raw material is heated to 230~600 °C, the firing time is controlled at 0.5~5h, and the clinker containing ammonium aluminum sulfate and ammonia gas are prepared. The ammonia gas is used to prepare ammonia water or pass into ammonium aluminum sulfate. Eluate decomposition process;

Clinker dissolution: The cooked clinker is eluted with hot water or washing solution, the dissolution time is 0.1~5h, the dissolution time can also be 0.1~2h, aluminum enters the solution in the form of aluminum ammonium silicate, and the silicon remains in the residue. Forming high silicon slag;

Ammonia gas recovery: The ammonia gas generated during the clinker burning process is recovered by water or washing liquid, or sent to the aluminum sulfate ammonium solution decomposition process by a compressor after dust removal;

Separation and washing of high silicon slag: The slurry after dissolution is subjected to solid-liquid separation and washing, the solution is ammonium aluminum sulfate solution, and the washed slag is high silicon slag;

Decomposition of ammonium alginate solution: Ammonia or ammonia water obtained by an ammonia gas recovery step is added to the ammonium aluminum silicate solution to obtain a crude aluminum hydroxide and ammonium sulfate solution containing impurities;

Separation and washing of crude aluminum hydroxide: The slurry after decomposition of ammonium aluminum sulfate is subjected to solid-liquid separation and washing with crude aluminum hydroxide, the liquid is ammonium sulfate solution, and the solid is crude aluminum hydroxide;

Desulfurization of crude aluminum hydroxide: The crude aluminum hydroxide obtained by the decomposition of ammonium aluminum sulfate solution contains a large amount of sulfate, which will react with caustic in the subsequent Bayer process and dissolution process, causing a large amount of alkali loss, and using an alkaline solution. Desulfurization is carried out to obtain crude sulfate-free aluminum hydroxide (desulfated crude aluminum hydroxide);

Low-temperature Bayer treatment: Desulfurization of crude aluminum hydroxide is carried out by low-temperature Bayer process with circulating alkali solution to remove impurities such as iron and calcium to obtain metallurgical grade alumina and high iron slag; ammonium sulfate solution evaporation: sulfuric acid separated by aluminum hydroxide The ammonium solution is evaporated to obtain a suitable ammonium sulfate solution or ammonium sulfate crystals.

The raw meal is prepared by mixing fly ash with ammonium sulphate by direct mixing or grinding, and the grinding and mixing can be carried out by wet or dry grinding.

The clinker is eluted by one of a mill dissolution or a stirred solution, and the mill is dissolved by using one of a grinding solution or a two-stage grinding solution, and the mixture is stirred and dissolved by one of intermittent stirring or continuous stirring.

The high silicon slag separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.

The high silicon slag separation wash is one of primary, secondary or multistage countercurrent washing. The ammonium aluminum sulfate eluate is decomposed by one of decomposing ammonia gas or decomposing ammonia water, and the ammonia gas or ammonia water is recovered from tail gas ammonia generated by the clinker burning process. The crude aluminum hydroxide separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.

The crude aluminum hydroxide is desulfurized by using one of sodium carbonate, sodium hydroxide, lime milk or ammonia water as a desulfurizing agent.

The desulfurized crude aluminum hydroxide separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.

The Bayer process for treating desulfurized crude aluminum hydroxide is a full Bayer process for producing alumina, including raw slurry preparation, low temperature dissolution, red mud separation washing, sodium aluminate solution decomposition, aluminum hydroxide separation washing, hydrogen Process of alumina roasting and circulating alkali evaporation and blending. The low temperature dissolution conditions are temperature 85~180 °C, circulating alkali concentration 100~220g/L, and dissolution time 10~90min. The red mud separation washing employs one of vacuum separation, sedimentation separation or pressurized separation. The sodium aluminate solution is decomposed by one of decomposition or two-stage decomposition, and the decomposition rate is 35 to 55%. The aluminum hydroxide separation washing employs one of vacuum separation, sedimentation separation or pressurized separation. The aluminum hydroxide is calcined by one of rotary kiln roasting, fluidized roasting or gaseous suspension roasting. The circulating mother liquor is evaporated and formulated using one or a combination of falling film evaporation, forced circulation steaming or natural circulation evaporation.

The product alumina is alumina that meets metallurgical grade requirements.

The ammonium sulfate is evaporated by one or a combination of falling film evaporation, forced circulation steaming or natural circulation evaporation.

The ammonium sulfate crystal produced by evaporation of the ammonium sulfate solution is one of centrifugal separation, vacuum separation, sedimentation separation or pressurized separation.

The high silicon slag is mainly composed of silica and is used to prepare white carbon, silica gel or other high silicon products.

The high iron slag is used as a raw material for iron making.

Advantageous Effects of the Invention: The invention does not add any auxiliary agent, and the fly ash does not need high temperature roasting activation, and can effectively extract alumina in the fly ash, and the extraction rate of the alumina can reach more than 85%, through the Bayer process. Low-temperature dissolution of seed decomposition and other processes produce metallurgical grade sand-like alumina that meets the requirements of the electrolytic aluminum industry, and successfully solves the problem of sulfuric acid containing aluminum hydroxide or ammonia precipitated aluminum hydroxide, greatly reducing alkali dissolution or Bayer process. Alkali consumption of dissolution. In the process of the invention, the ammonium sulfate cycle is realized, and the alumina in the fly ash can be extracted by batch batching through the circulation, and the exhaust gas and the waste liquid are not discharged in the whole process, and the main component of the high silicon slag after the fly ash is extracted from the alumina is Silica, easy to use, high iron slag can be used as ironmaking raw material Supply to the iron industry. The reaction system of the invention is a weak acid system, and the equipment is easy to solve, which is beneficial to industrialization. DRAWINGS

1 is a schematic flow chart of a process (Examples 1 - 6) of the present invention; and FIG. 2 is a flow chart of another alternative process (Examples 7 - 12) of the present invention. detailed description

Example 1

The composition of the raw material fly ash is: A1 ₂ 0 ₃ : 41%, Si0 ₂ : 48%, Fe ₂ 0 ₃ : 3.3%, CaO:

3.3%, Ti0 ₂ : 1.3%, MgO: 0.2%. The constituents of the raw material fly ash may also be other constituents, which are not intended to limit the scope of protection of the present invention.

1000g of fly ash of the above composition is taken, and the fly ash and the ammonium sulfate solution are mixed and wet-ground to obtain a raw material, wherein the weight ratio of ammonium sulfate to alumina in the fly ash is 5:1; the raw material is heated to 450 ° C, heat preservation lh, made clinker containing ammonium aluminum sulfate and ammonia gas, ammonia gas is used to prepare ammonia water or into ammonium aluminum sulfate solution; fired clinker is dissolved in hot water by wet grinding for 0.5h, aluminum The solution enters the solution in the form of aluminum ammonium silicate, and the silicon remains in the residue to form a high silicon slag; after the dissolution, the slurry is separated by a settling tank and washed in a three-stage countercurrent, the liquid is an ammonium aluminum silicate solution, and the solid is a high silicon slag; The ammonia solution produced by the clinking of the clinker is passed into the aluminum ammonium solution to decompose the solution into a crude aluminum hydroxide solid, and the liquid is an ammonium sulfate solution; after the decomposition, the slurry is separated and washed by a filter to obtain a crude aluminum hydroxide solid and an ammonium sulphate. The solution; the ammonium acid solution is evaporated to obtain an ammonium sulfate solution, which is returned to the raw material for grinding and recycling; the crude aluminum hydroxide is treated by low temperature Bayer process to obtain metallurgical grade alumina and high iron slag. The obtained products are metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash is 90%.

Example 2

1000g of the raw material fly ash in the first embodiment, 1000 g of the raw material fly ash and ammonium sulfate crystals are mixed and dry to obtain a raw material, wherein the weight ratio of ammonium sulfate to alumina in the fly ash is 6:1; Heating to 600 ° C, heat preservation for 5h, making clinker containing ammonium aluminum sulfate and ammonia gas, ammonia gas is used to prepare ammonia water or into ammonium aluminum sulfate solution; clinker is dissolved in hot water by wet grinding lh, aluminum The solution enters the solution in the form of ammonium aluminate, and the silicon remains in the residue to form a high silicon slag; after the dissolution, the slurry is separated by a settling tank and washed by a two-stage countercurrent, the liquid is an ammonium aluminum sulfate solution, and the solid is a high silicon slag; The ammonia solution is passed into the ammonium solution to generate ammonia gas, and the solution is decomposed into crude hydrogen. Alumina solid, the liquid is ammonium sulfate solution; after decomposition, the slurry is separated and washed by a filter to obtain a crude aluminum hydroxide solid and an ammonium sulfate solution; after the ammonium citrate solution is evaporated, an ammonium sulfate solution is returned to the raw material for grinding and recycling; The crude aluminum hydroxide is treated by low temperature Bayer process to obtain metallurgical grade alumina and high iron slag. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 92%.

Example 3

Take 1000g of the raw material fly ash in the first embodiment, and mix the fly ash with the ammonium sulfate solution to obtain the raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 7:1; The material is heated to 230 ° C, and kept for 3 hours to prepare clinker containing ammonium aluminum sulfate and ammonia gas. The ammonia gas is used to prepare ammonia water or into ammonium aluminum sulfate solution; the clinker is dissolved in hot water for 2 hours by wet grinding. The aluminum enters the solution in the form of ammonium aluminum sulfate, and the silicon remains in the residue to form high silicon slag; after the dissolution, the slurry is separated by a filter and washed by a first-stage countercurrent, the liquid is an ammonium aluminum phosphate solution, the solid is a high silicon slag; Ammonia water is added to the aluminum ammonium solution to dissolve the solution into a crude aluminum hydroxide solid, and the liquid is an ammonium sulfate solution; after decomposition, the slurry is separated and washed by a settling tank to obtain a crude aluminum hydroxide solid and an ammonium sulfate solution; After the ammonium sulfate solution is evaporated, the ammonium sulfate solution is returned to the raw material for grinding and recycling; the crude aluminum hydroxide is treated by low temperature Bayer process to obtain metallurgical grade alumina and high iron slag. The obtained products are metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash is 90%.

Example 4

Take 1000g of the raw material fly ash in the first embodiment, and mix the fly ash with the ammonium sulfate solution to dry the raw material to obtain the raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 8:1; The raw material is heated to 550 ° C, and kept for 0.5 h, and the clinker and ammonia gas containing the aluminum ammonium sulphate are prepared, and the ammonia gas is used for preparing ammonia water or into the ammonium aluminum sulfate solution; the clinker is stirred in the hot water After dissolution for 1.5h, aluminum enters the solution in the form of aluminum ammonium silicate, and silicon remains in the residue to form high silicon slag. After dissolution, the slurry is separated by sedimentation tank and washed by three-stage advection. The liquid is ammonium aluminum sulfate solution and the solid is high silicon. The slag is added to the ammonium aluminum sulfate solution to dissolve the ammonia water produced by the clinker, and the solution is decomposed into a crude aluminum hydroxide solid, and the liquid is a rock ammonium acid solution; after the decomposition, the slurry is separated and washed by a filter to obtain a crude aluminum hydroxide solid. And ammonium sulfate solution; ammonium sulfate solution is evaporated to obtain ammonium sulfate crystals, which are returned to the raw material for grinding and recycling; the crude aluminum hydroxide is treated by low temperature Bayer process to obtain metallurgical grade alumina and high iron slag. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 91%.

Example 5 Take 1000g of the raw material fly ash in the first embodiment, and mix the fly ash with the ammonium sulfate solution to dry the raw material to obtain the raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is

4.5 : 1 ; The raw material is heated to 40 CTC and kept for 1.5 h to prepare clinker containing ammonium aluminum sulfate and ammonia gas. The ammonia gas is used to prepare ammonia water or into ammonium aluminum sulfate solution; clinker is used in hot water. After stirring, O. lh, aluminum enters the solution in the form of ammonium aluminum sulfate, and silicon remains in the residue to form high silicon slag. After dissolution, the slurry is separated by sedimentation tank and washed by two-stage countercurrent. The liquid is ammonium aluminum sulphate solution, and the solid is High silicon slag; adding ammonia water produced by clinking of the clinker to the ammonium aluminum sulfate solution, decomposing the solution into a crude aluminum hydroxide solid, and the liquid is an ammonium sulfate solution; after decomposing, the slurry is separated and washed by a filter to obtain a crude aluminum hydroxide solid. And ammonium sulfate solution; ammonium sulfate solution is evaporated to obtain ammonium sulfate crystals, which are returned to the raw material for grinding and recycling; the crude aluminum hydroxide is treated by low temperature Bayer process to obtain metallurgical grade alumina and high iron slag. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 93%.

Example 6

Take 100g of the raw material fly ash in the first embodiment, and mix the fly ash with the ammonium sulfate solution to dry the raw material to obtain the raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 4.5:1; The raw material is heated to 400 ° C and kept for 1.5 h to prepare clinker containing ammonium aluminum sulfate and ammonia gas. The ammonia gas is used to prepare ammonia water or into ammonium aluminum sulfate solution; the clinker is dissolved in hot water by stirring. Lh, aluminum enters the solution in the form of ammonium aluminum sulfate, and silicon remains in the residue to form high silicon slag; after dissolution, the slurry is separated by sedimentation tank and washed by a first-stage advection, the liquid is ammonium aluminum sulphate solution, and the solid is high silicon slag Adding ammonia water produced by clinking the clinker to the ammonium aluminum sulfate solution, decomposing the solution into a crude aluminum hydroxide solid, and the liquid is an ammonium citrate solution; after decomposing, the slurry is separated and washed by a filter to obtain a crude aluminum hydroxide solid and sulfuric acid. Ammonium solution; ammonium sulfate solution is evaporated to obtain ammonium sulfate crystals, which are returned to the raw material for grinding and recycling; crude aluminum hydroxide is treated by low temperature Bayer process to obtain metallurgical grade alumina and high iron slag. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 91%.

Example 7

Take 1000g of the raw material fly ash in the first embodiment, and mix the fly ash with the ammonium ammonium carbonate solution to obtain the raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 5:1; Heating to 450 °C, keeping lh, making clinker containing ammonium aluminum sulfate and ammonia gas, ammonia is used to recover ammonia water by water recovery; the clinker is fired in hot water for 0.5h, using a grinding machine for 0.5h, aluminum is sulfuric acid The form of aluminum ammonium enters the solution, and the silicon remains in the residue to form high silicon slag; after the dissolution, the slurry is separated by a settling tank and washed in a three-stage countercurrent, the liquid is an ammonium aluminum sulfate solution, and the solid is a high silicon slag; Adding ammonia water recovered from ammonia gas generated by clinking of clinker to the ammonium aluminum sulfate solution, decomposing the solution to obtain a crude aluminum hydroxide slurry, using vacuum separation and washing, the solid is crude aluminum hydroxide, and the liquid is ammonium sulfate solution; The slurry is washed by vacuum separation to obtain a crude aluminum hydroxide solid and an ammonium sulfate solution; the crude aluminum hydroxide is desulfurized by using sodium carbonate to obtain a desulfurized crude aluminum hydroxide slurry, which is subjected to vacuum separation and washing to obtain sulfur-free crude aluminum hydroxide; ammonium sulfate The solution is prepared by falling film evaporation, and the ammonium sulfate solution is returned to the raw material for preparation and recycling; the sulfur-free aluminum hydroxide is prepared by the original slurry, low-temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation washing, and hydration Aluminum roasting and circulating alkali liquid evaporation and blending, low temperature dissolution conditions are temperature 85 ° C, circulating alkali concentration 220 g / L, dissolution time 60 min, red mud separation washing using sedimentation separation, sodium aluminate solution decomposition using a decomposition, decomposition The rate is 50%, the separation and washing of aluminum hydroxide is vacuum separation, and the aluminum hydroxide roasting is performed by rotary kiln roasting. The mother liquor was evaporated and the formulation using a falling film evaporator. The obtained products are metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash is 90%.

Example 8

1000g of the raw material fly ash in the first embodiment is taken, and the fly ash and the ammonium sulfate solution are mixed and dry-milled to obtain a raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 6:1; the raw material is heated to 60CTC, heat preservation for 3h, making clinker containing ammonium aluminum sulfate and ammonia gas, ammonia gas is washed by washing liquid to prepare ammonia water; fired clinker is dissolved in hot water in two stages of mill for lh, aluminum is aluminum sulfate The form enters the solution, and the silicon remains in the residue to form a high silicon slag; after the dissolution, the slurry is separated by a settling tank and washed by a secondary countercurrent, the liquid is an ammonium aluminum sulfate solution, the solid is a high silicon slag; and the clinker is added to the ammonium aluminum sulfate solution. The ammonia water recovered by the produced ammonia gas is decomposed to obtain a crude aluminum hydroxide slurry, which is separated and washed by vacuum, and the solid is crude aluminum hydroxide, and the liquid is ammonium sulfate solution; after decomposition, the slurry is washed and separated by pressure to obtain coarse Aluminium hydroxide solid and ammonium sulphate solution; crude aluminum hydroxide is desulfurized by sodium hydroxide to obtain a desulfurized crude aluminum hydroxide slurry, which is obtained by pressure separation and washing to obtain sulfur-free crude aluminum hydroxide; After falling film evaporation, the ammonium sulfate is returned to the raw material by centrifugal filtration to prepare and recycle; the sulfur-free aluminum hydroxide is prepared by the original slurry, low-temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation and washing, hydrogen Alumina roasting and circulating alkali evaporation and blending, low temperature dissolution conditions are temperature 120 °C, circulating alkali concentration 170g / L, dissolution time 20min, red mud separation washing with pressure separation, sodium aluminate solution decomposition using a section Decomposition, decomposition rate 40%, aluminum hydroxide separation washing using sedimentation separation, aluminum hydroxide roasting using gaseous suspension roasting, circulation mother liquid evaporation and blending using falling film evaporation and forced circulation evaporation combination. owned The products are metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash is 92%.

Example 9

Take 1000g of the raw material fly ash in the first embodiment, and directly mix the fly ash with the ammonium sulfate solution to obtain a raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 7:1; the raw material is heated to 230 °C, keep warm for 5h, make clinker containing ammonium aluminum sulfate and ammonia gas, ammonia gas is sent to the process of decomposition of ammonium aluminum sulfate eluate by compressor after dust removal; the clinker is fired and dissolved in hot water with intermittent stirring 5h, aluminum enters the solution in the form of ammonium aluminum sulfate, and the silicon remains in the residue to form high silicon slag. After the dissolution, the slurry is washed by vacuum separation, the liquid is ammonium aluminum sulfate solution, and the solid is high silicon slag; added to the ammonium aluminum sulfate solution The ammonia water recovered from the ammonia produced by the clinker is decomposed to obtain a crude aluminum hydroxide slurry, which is separated and washed by pressure, and the solid is crude aluminum hydroxide, and the liquid is ammonium sulfate solution; after decomposition, the slurry is washed and separated by vacuum. , obtaining crude aluminum hydroxide solid and ammonium sulfate solution; crude aluminum hydroxide is desulfurized by using sodium hydroxide to obtain a desulfurized crude aluminum hydroxide slurry, and the sulfur-free crude hydrogen oxygen is obtained by pressure separation and washing. After the evaporation of falling film is carried out, the ammonium sulfate solution is separated by centrifugal separation to obtain ammonium sulfate and returned to the raw material for preparation and recycling; the sulfur-free aluminum hydroxide is prepared by the original slurry, low-temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, hydrogen Alumina separation washing, aluminum hydroxide roasting and circulating alkali evaporation and blending, low temperature dissolution conditions are temperature 100 °C, circulating alkali concentration 200g/L, dissolution time 20min, red mud separation washing using vacuum separation, sodium aluminate The solution is decomposed by two-stage decomposition with a decomposition rate of 55%. The separation and washing of aluminum hydroxide is carried out by pressure separation. The aluminum hydroxide roasting is carried out by fluidized roasting, and the circulation mother liquid is evaporated and blended by forced circulation evaporation. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 92%.

Example 10

1000g of the raw material fly ash in the first embodiment is taken, and the fly ash and the ammonium sulfate solution are mixed and dry-milled to obtain a raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 8:1; the raw material is heated to 550 °C, heat preservation 0.5h, made clinker containing ammonium aluminum sulfate and ammonia gas, ammonia gas is washed by washing liquid to prepare ammonia water; fired clinker is dissolved in hot water for 1.5h with continuous stirring, aluminum is aluminum sulfate The form of ammonium enters the solution, and the silicon remains in the residue to form high silicon slag; after the dissolution, the slurry is washed and separated by pressure, the liquid is ammonium aluminum sulfate solution, the solid is high silicon slag; the clinker is added to the ammonium aluminum sulfate solution to produce The ammonia water recovered by the ammonia gas is decomposed to obtain a crude aluminum hydroxide slurry, which is separated and washed by vacuum, and the solid is crude aluminum hydroxide, and the liquid is ammonium sulfate solution; after decomposition, the slurry is subjected to sedimentation separation and washing to obtain crude aluminum hydroxide. Solid and sulfuric acid Ammonium solution; crude aluminum hydroxide is desulfurized by sodium hydroxide to obtain a desulfurized crude aluminum hydroxide slurry, which is separated and washed to obtain sulfur-free crude aluminum hydroxide; ammonium sulfate solution is combined by falling film evaporation and forced circulation evaporation. Pressurization separation to obtain ammonium sulfate return raw material preparation, recycling; sulfur-free aluminum hydroxide through raw slurry preparation, low temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation washing, aluminum hydroxide roasting and circulation Alkaline evaporation and blending, low temperature dissolution conditions are temperature 160 ° C, circulating alkali concentration 150 g / L, dissolution time 50 min, red mud separation washing using pressure separation, sodium aluminate solution decomposition using a decomposition, decomposition rate 35% The separation and washing of aluminum hydroxide is carried out by vacuum separation, the aluminum hydroxide roasting is carried out by gaseous suspension roasting, the circulating mother liquid is evaporated and the preparation is carried out by natural circulation circulation evaporation. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 91%.

Example 11

1000g of the raw material fly ash in the first embodiment is taken, and the fly ash and the ammonium sulfate solution are mixed and wet-ground to obtain a raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 4.5:1; the raw material is heated to Lh, aluminium sulphate is sulphuric acid. The sulphuric acid is sulphuric acid. The sulphuric acid is sulphuric acid. The form of aluminum ammonium enters the solution, and the silicon remains in the residue to form high silicon slag; after the dissolution, the slurry is washed and separated by pressure, the liquid is ammonium aluminum sulfate solution, the solid is high silicon slag; the clinker is added to the ammonium aluminum sulfate solution. The ammonia water recovered by the ammonia gas is recovered, and the solution is decomposed to obtain a crude aluminum hydroxide slurry, which is separated and washed by vacuum. The solid is crude aluminum hydroxide, and the liquid is ammonium sulphate solution; after decomposition, the slurry is washed by vacuum to obtain coarse Aluminum hydroxide solid and ammonium sulfate solution; crude aluminum hydroxide is desulfurized with ammonia water to obtain a desulfurized crude aluminum hydroxide slurry, which is separated and washed to obtain sulfur-free crude aluminum hydroxide; After natural circulation evaporation, the ammonium sulfate is returned to the raw material by pressure separation to prepare and recycle; the sulfur-free aluminum hydroxide is prepared by the original slurry, low-temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation and washing, Aluminum hydroxide roasting and circulating alkali liquid evaporation and blending, low temperature dissolution conditions are temperature 180 ° C, circulating alkali concentration 130 g / L, dissolution time 40 min, red mud separation washing using vacuum separation, sodium aluminate solution decomposition using two stages Decomposition, decomposition rate 45%, aluminum hydroxide separation and washing using vacuum separation, aluminum hydroxide roasting using gaseous suspension roasting, circulating mother liquor evaporation and blending using natural circulation evaporation. The obtained products are metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash is 90%.

Example 12 Take 1000g of the raw material fly ash in the first embodiment, and mix the fly ash with the ammonium sulfate solution to obtain a raw material, wherein the weight ratio of the ammonium sulfate to the alumina in the fly ash is 5:1; the raw material is heated to 400 ° C, heat preservation 2h, made clinker containing ammonium aluminum sulfate and ammonia gas, ammonia gas is washed with washing liquid to prepare ammonia water; fired clinker in hot water with continuous stirring for 0.5h, aluminum with aluminum sulfate The form enters the solution, and the silicon remains in the residue to form a high silicon slag; after the dissolution, the slurry is washed and separated by pressure, the liquid is an ammonium aluminum sulphate solution, and the solid is a high silicon slag; the clinker is added to the ammonium sulphate solution The ammonia water recovered by the ammonia generated by the calcination is decomposed to obtain a crude aluminum hydroxide slurry, which is separated and washed by vacuum, and the solid is crude aluminum hydroxide, and the liquid is ammonium sulfate solution; after decomposition, the slurry is washed by vacuum separation to obtain coarse Aluminum hydroxide solid and ammonium sulfate solution; crude aluminum hydroxide is dehydrated by using lime milk to obtain de-saturated crude aluminum hydroxide slurry, using sedimentation separation and washing to obtain sulfur-free crude aluminum hydroxide; ammonium sulfate solution adopting falling film evaporation The ammonium sulfate is returned to the raw material by pressure separation to prepare and recycle; the sulfur-free aluminum hydroxide is prepared by the original slurry, low-temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation washing, aluminum hydroxide roasting And circulating alkali liquid evaporation and blending, low temperature dissolution conditions are temperature 180 ° C, circulating alkali concentration 130g / L, dissolution time 40min, red mud separation washing using vacuum separation, sodium aluminate solution decomposition using two-stage decomposition, decomposition rate 50%, aluminum hydroxide separation and washing using vacuum separation, aluminum hydroxide roasting using gaseous suspension roasting, circulation mother liquid evaporation and blending using falling film evaporation. The obtained products were metallurgical grade alumina alumina and high iron slag (red mud), and the alumina extraction rate in fly ash was 92%.

In the above embodiment, the Bayer process is used to treat the crude aluminum hydroxide as the whole Bayer process for producing alumina, including raw slurry preparation, low temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation washing and hydration. Aluminum baking and other processes; the main component of the obtained high silicon slag is silica, which is used for preparing white carbon black, silica gel or other high silicon products; high iron slag can be used as ironmaking raw material.

The specific embodiments of the present invention have been described above by way of example, but the scope of the invention is defined by the following claims and not limited by the embodiments of the invention.

Claims

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An ammonia process for treating fly ash to produce alumina, characterized by comprising the steps of:

Raw material grinding: mixing fly ash with ammonium sulfate, grinding into raw material, wherein the weight ratio of ammonium sulfate to alumina in fly ash is 4.5 ~ 8: 1;

Clinking of clinker: The raw material is heated to 230~600 °C, the firing time is controlled at 0.5~5h, and the clinker containing ammonium aluminum sulfate and ammonia gas are prepared. The ammonia gas is used to prepare ammonia water or pass into ammonium aluminum sulfate. In solution

Clinker dissolution: The cooked clinker is dissolved in hot water, and the dissolution time is 0.:! ~ 2h, aluminum enters the solution in the form of ammonium aluminum sulfate, and silicon remains in the residue to form high silicon slag;

Ammonia gas recovery: The ammonia gas generated during the clinker burning process is recovered by water or washing liquid, or sent to the decomposition process by a compressor after dust removal;

Decomposition of ammonium aluminum sulfate solution: adding ammonia gas or ammonia water obtained by a clinker baking process to an ammonium aluminum sulfate solution to obtain a crude aluminum hydroxide and ammonium sulfate solution containing impurities;

Separation and washing of crude aluminum hydroxide: The slurry after decomposition of ammonium aluminum sulfate is subjected to solid-liquid separation and washing with crude aluminum hydroxide, and the liquid is a solution of ammonium sulfate in acid, and the solid is crude aluminum hydroxide;

Low-temperature Bayer treatment: The crude aluminum hydroxide is treated with a circulating alkali solution at a low temperature Bayer process to remove impurities such as iron and calcium to obtain metallurgical grade alumina and high iron slag;

Evaporation of ammonium sulfate solution: The ammonium sulfate solution obtained by separating aluminum hydroxide is evaporated to obtain an ammonium sulfate solution or an ammonium sulfate crystal which is suitable for compounding.

The method for producing alumina by the ammonia method for treating fly ash according to claim 1, wherein the raw material grinding is one of wet grinding or dry grinding.

The method for producing alumina by the ammonia method for treating fly ash according to claim 1, wherein the clinker is eluted by one of wet milling or stirred dissolution.

The method for producing alumina by the ammonia method for treating fly ash according to claim 1, characterized in that the high-silicon slag separation washing adopts one of a filter separation or a settling tank separation.

5. The method for treating alumina from fly ash by ammonia method according to claim 1, characterized in that the high silicon slag separation washing adopts one-stage, two-stage or multi-stage countercurrent washing or mining. One of the first, second or multistage advection washings.

The method for producing alumina by the ammonia method for treating fly ash according to claim 1, wherein the aluminum aluminophosphate is decomposed by one of ammonia gas decomposition or ammonia hydrolysis.

A method of producing alumina by the ammonia process for treating fly ash according to claim 1, wherein said aluminum hydroxide separation washing employs one of a filter separation or a settling tank separation.

8. The method for treating alumina from fly ash by ammonia method according to claim 1, characterized in that the Bayer process is used to treat crude aluminum hydroxide as a whole Bayer process for producing alumina, including raw pulp blending. 4, warm dissolution, red mud separation washing, sodium aluminate solution decomposition, aluminum hydroxide separation washing and aluminum hydroxide roasting and other processes.

9. The method for treating alumina from fly ash according to claim 1, wherein the high silicon slag is mainly composed of silica for preparing white carbon, silica gel or other high silicon. product.

The method for producing alumina by the ammonia method for treating fly ash according to claim 1, wherein the high iron slag is used as a raw material for iron making.

1 1. A method for treating alumina from fly ash by ammonia process, comprising the steps of:

Raw material preparation: mixing fly ash with ammonium sulfate to prepare raw material, wherein the weight ratio of ammonium sulfate to alumina in fly ash is 4.5 ~ 8:1;

Clinking of clinker: The raw material is heated to 230~600 °C, the firing time is controlled at 0.5~5h, and the clinker containing ammonium aluminum sulfate and ammonia gas are prepared. The ammonia gas is used to prepare ammonia water or pass into ammonium aluminum sulfate. Eluate decomposition process;

Clinker dissolution: The cooked clinker is eluted with hot water or washing solution, the dissolution time is 0.1~5h, aluminum enters the solution in the form of ammonium aluminum sulfate, and the silicon remains in the residue to form high silicon slag;

Ammonia gas recovery: The ammonia gas generated during the clinker burning process is recovered by water or washing liquid, or sent to the aluminum aluminum citrate dissolution solution by a compressor after dust removal;

Decomposition of ammonium aluminum sulfate solution: ammonia or ammonia water obtained by an ammonia gas recovery step is added to the ammonium aluminum sulfate solution to obtain a crude aluminum hydroxide and ammonium sulfate solution containing impurities;

Separation and washing of crude aluminum hydroxide: The slurry after decomposition of ammonium aluminum sulfate is subjected to solid-liquid separation and coarse Aluminium hydroxide washing, the liquid is ammonium sulfate solution, the solid is crude aluminum hydroxide; the crude aluminum hydroxide is desulfurized: the crude aluminum hydroxide obtained by the decomposition of the aluminum ammonium silicate solution contains a large amount of sulfate, in the subsequent Bayer process and During the dissolution process, it will react with caustic alkali, causing a large amount of alkali loss. The dehydrated solution is used to remove the acid-free 4 艮 crude aluminum hydroxide; low temperature Bayer treatment: desulfurization of crude aluminum hydroxide with circulating alkali solution for low temperature Bayer process Processing, removing impurities such as iron and calcium to obtain metallurgical grade alumina and high iron slag; evaporation of ammonium sulfate solution: The ammonium sulfate solution obtained by separating aluminum hydroxide is evaporated to obtain a suitable ammonium sulfate solution or ammonium sulfate crystal.

12. The method for treating alumina from fly ash by the ammonia method according to claim 1, wherein the raw material is prepared by directly mixing or grinding and mixing the fly ash with stone, ammonium acid. Mix together.

13. A method of ammonia processing fly ash to produce alumina according to claim 12, characterized in that said grinding mixing is carried out by wet or dry milling.

14. The method for treating alumina from fly ash by an ammonia process according to claim 1, wherein the clinker is eluted by one of a mill dissolution or a stirred solution.

15. The method of claim 14, wherein the slurry is eluted by one of a set of grinding or two stages of grinding.

The method for producing alumina by the ammonia method for treating fly ash according to claim 14, wherein the agitation dissolution is one of intermittent stirring dissolution or continuous stirring dissolution.

17. The method of treating alumina from fly ash by an ammonia process according to claim 1, wherein said high silicon slag separation washing is one of vacuum separation, sedimentation separation or pressurized separation.

18. The method according to claim 1, wherein the high silicon slag separation washing adopts one of primary, secondary or multistage countercurrent washing.

19. The method for producing alumina by treating ammonia fly ash according to claim 1, wherein the ammonium aluminum sulfate eluate is decomposed by one of decomposing ammonia gas or adding ammonia water.

20. The method of ammonia processing fly ash to produce alumina according to claim 19, wherein the ammonia gas or ammonia water is derived from tail gas ammonia recovery generated by the clinker firing step.

21. The method for treating alumina from fly ash by an ammonia process according to claim 1 1 It is characterized in that the crude aluminum hydroxide separation washing adopts one of vacuum separation, sedimentation separation or pressure separation.

22. The method for treating alumina from fly ash by the ammonia method according to claim 11, wherein the crude aluminum hydroxide is desulfurized by using one of sodium carbonate, sodium hydroxide, lime milk or ammonia water. Depurinating agent.

23. The method for treating alumina from fly ash by an ammonia process according to claim 1, wherein the desulfurized crude aluminum hydroxide is separated and washed by vacuum separation, sedimentation separation or pressurized separation.

24. The method for treating alumina from fly ash by the ammonia method according to claim 11, wherein the method for treating desulfurized crude aluminum hydroxide by using the Bayer process is a full Bayer process for producing alumina, including the original Slurry preparation, low temperature dissolution, red mud separation and washing, sodium aluminate solution decomposition, aluminum hydroxide separation and washing, aluminum hydroxide roasting, circulating alkali evaporation and blending.

25. The method for ammonia processing fly ash to produce alumina according to claim 24, wherein the low temperature dissolution condition is a temperature of 85 to 18 (TC, circulating alkali concentration)

100-22 Og/L, dissolution time 10~90min.

26. The method of ammonia treating fly ash to produce alumina according to claim 24, wherein the red mud separation washing is one of vacuum separation, sedimentation separation or pressurized separation.

27. The method according to claim 24, wherein the sodium aluminate solution is decomposed by one of decomposition or two decomposition, and the decomposition rate is 35 to 55%. .

28. The method of ammonia treating fly ash to produce alumina according to claim 24, wherein the aluminum hydroxide separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.

The method for producing alumina by the ammonia treatment of fly ash according to claim 24, characterized in that the aluminum hydroxide is calcined by one of rotary kiln roasting, fluidized roasting or gaseous suspension roasting.

30. The method for ammonia processing fly ash to produce alumina according to claim 24, wherein the circulating mother liquor is evaporated and formulated using one or more of falling film evaporation, forced circulation steaming or natural circulation evaporation. Combination of species.

31. The method of ammonia processing a fly ash to produce alumina according to claim 24, It is characterized in that the product alumina is alumina which meets the requirements of metallurgical grade.

32. The method of claim 1, wherein the ammonium sulfate is vaporized by one or more of falling film evaporation, forced circulation steaming, or natural circulation evaporation. The combination.

33. The method of claim 1, wherein the ammonium sulfate crystal produced by evaporation of the ammonium sulfate solution is subjected to centrifugal separation, vacuum separation, sedimentation separation or pressure separation. One of them.

34. The method of claim 1, wherein the high silicon slag is mainly composed of silica and is used to prepare white carbon, silica gel or other high. Silicon products.

35. A method of producing alumina from a fly ash by an ammonia process according to claim 1 1 , characterized in that said high iron slag is used as a raw material for iron making.